Climate change is going to increase that number further, according to the study in the Internal Medicine Journal. The increased greenhouse gas emissions over the past century caused changes in our climate system, most notably the warming of the atmosphere and oceans.

An increase in natural weather-related disasters, changes in rainfall patterns, more frequent heatwaves and warmer temperatures. All of these effects affect the environment and also human health in various ways, the study finds.

Rising temperatures and emissions, for example, results in an increase in pollen yields in many plants, meaning higher pollen concentrations and longer pollen seasons, which could increase the frequency and severity of pollen allergies.